Electrotype printing plate and method of producing the same



Nov. 19, 1940. a ATWOOD 2,222,013

ELECTROTYPE PRINTING PLATE AND METHOD OF PRODUCING THE SAME Filed Jan. 21, 1939 Patented Nov. 19, 1940 UNITED STATES ELECTROTYPE PRINTING PLATE AND DIETHOD OF PRODUCING THE SAME.

Benjamin F. Atwood, Boston, Mass., assignor to Back Bay Electrotype and Engraving 00., Boston, Mass., a corporation of Massachusetts Application January 21, 1939, Serial No. 252,196

16 Claims.

The present invention relates to electrotype plates and to a process for producing the same.

In .the making of electrotype plates a thin metal shell of electrolytically deposited metal is placed face down in a backing up pan and molten backing metal is deposited on the back of the shell to give the plate substance. The backing up metal is principally lead or type metal.

With backing up processes now generally employed, it has been found that the leaden backing metal shrinks on cooling and exerts a shrinking or compressing force on the shell which results in a reduction in the size of the shell which amounts to about inch per foot. In the use of electrotypes for printing dials, maps and other multi-color work where perfect registry is essential, this shrinkage of the shells becomes very important because inevitable variation in the degree of shrinkage between different plates makes accurate registry of the impressions difllcult if not impossible in some instances.

Although this shrinkage problem has been recognized for many years in the electrotyping industry, no satisfactory solution has been presented prior to the present invention.

I have found that the shrinking efiect of the backing metal on the electrotype shell can be controlled or neutralized entirely by embedding in the backing up metal an insert sheet of metal of proper composition and thickness and positioned adjacent the back of the shell while the backing metal is still in a molten state. A metal plate of proper composition and thickness embedded in the backing metal in contact with the shell may be employed to control or neutralize entirely dimensional changes in the shell due to the efiect of the backing metal in the production of the electrotype plate.

In order to control the shrinkage of the shell, the inserted metal plate must be of proper composition and thickness in relation to the thickness of the shell. If the embedded plate is not of the proper composition and thickness, shrinkage or distortion of the shell may be the result upon cooling of the backing up metal.

It is a primary object of the present invention to provide an improved electrotype plate and a process of forming the same in which shrinkage is neutralized in the backing up of the electrotype shell.

Another object of the invention is to provide a process for producing electrotype plates wherein the dimensional change in the electrotype shell is positively controlled.

A further object is to provide an electrotype plate having a metal insert plate embedded in the backing up metal in contact with the back of the electrotype shell and united thereto for the purpose of controlling dimensional change in the shell in the backing up operation.

Other objects and advantages of the invention will be apparent from the following description and upon reference to the accompanying drawing which are illustrative of the new process and the electrotype plate produced thereby.

In the drawing: a

Figure l is a plan view of a backlngpan during the operation of backing up an electrotype according to the invention,

Figure 2 is a sectional view taken on the line 2-2 of Figure 1, and

Figure 3. is an enlarged fragmentary detailedsectional view of a finished plate produced in accordance with the invention.

In the' practice of the process of producing electrotypes according to the invention, an electrotype shell I0 is placed-face down in a backing-up pan H. The pan Il may be of the usual construction for this purpose, except that it is preferably larger than that commonly employed so that the shell III will not cover the entire bottom of the pan. The back of the shell is tinned as indicated at l2, either before or after being placed in the pan, in the usual manner. With the tinned shell III in place, as shown, molten backing metal I3 is poured into the pan to a depth to form a backing of the desired thickness. The pan II is kept hot enough to maintain the backing etal in a molten state during'the next operation.

While the backing metal is still molten, a thin metal insert sheet l4, substantially the same size as the shell and preferably tinned on both sides, as indicated at I5, is immersed in the backing metal and moved into registry with the shell and heldv down in contact with the back of the shell while the backing metal solidifies and cools. The insert plate or sheet 14, which is formed of metal which is harder than and which has a higher melting point than the backing metal, is held in place during cooling of the backing metal by a frame II, provided with a plurality of depending pins [8 which dip into the molten metal and engage the back of the insert plate. A weight I9 is carried by the frame I! for weighting down the sheet I4. The backing up metal I3 is allowed to cool with the insert plate thus held in position against the back of the electrotype shell. The insert plate is thus embedded in the backing up metal and united to the back of the'electrotype shell by a very thin intervening layer l6 of backing metal.

In the step of inserting the insert plate into position in the molten backing metal, the plateis immersed in the molten metal at the end of the backing up pan removed from the end in which the shell is placed and the insert plate is then moved back and forth a number of times as it is lowered into position against the back of the shell to insure that all air bubbles are eliminated from beneath the plate. Any air trapped between the shell and insert plate would result in a soft spot in the printing surface.

In order to reduce or substantially eliminate change of dimension of the shell in the backing of electrotypes, it has been found that an insert plate or sheet of proper thickness in relation to the thickness of the shell is essential. If the insert sheet is too thin, shrinkage is not-eliminated and if the sheet is too thick distortion or undue expansion of the shell may be the result.

As an example of the practice of the invention in the backing up of a XX copper electrotype shell .020 of an inch in thickness, the shell, tinned on the back, is placed in one end of a backing pan face down and the molten backing metal then poured into the pan on top of the shell to a depth of about of an inch. While the backing metal is still in a molten state, a copper sheet approximately the same size as the shell and of the order of about .019 to .020 of an inch in thickness, tinned on both sides, is carefully immersed in the molten backing metal, moved back and forth therein a number of times to eliminate any air bubbles trapped beneath the copper sheet, and then moved into registry with the shell and pressed down into engagement with the back of the shell, being retained in this position by the weighted frame I! and pins l8 during solidification and cooling of the backing metal. After solidification of the backing metal, the weighted frame is removed, the pins I8 being readily withdrawn from the backing, and the electrotype plate is trimmed and finished in the usual manner. There will be no change in the dimension of the shell after backing.

As another example, the process above outlined is duplicated except that the insert sheet is formed of half-hard brass .020 of an inch in thickness. No change in dimension of the shell due to the backing up operation occurs.

As another example the same process is followed except that a sheet of tin plate .015 of an inch in thickness may be employed as the insert plate. No shrinkage of the shell due to the backing up operation occurs.

As another example a sheet of tin plate .020 of an inch in thickness may be substituted for the copper plate. In the resultant electrotype plate, the shell will be found to. be expanded by .007 of an inch per foot of shell.

As another example a phosphor bronze plate .020 of an inch in thickness may be substituted for the copper plate. In the resultant electrotype plate, the shell will be found to have been shrunk by .002 of an inch per foot of shell.

As a further example a german silver plate .020 inch in thickness may be substituted for the copper insert plate. In the resultant-electrotype plate, the shell will be found to have been expanded by .001 of an inch per foot of shell.

In the examples given by way of illustration, exact relative dimensions of shell and insert plate thickness employed to effect certain results have been given, however, satisfactory control within ranges suitable for most cases will result when the relative thickness of the shell and insert plate are varied to some extent. For instance where some tolerance is permissible in the finished printing member, the insert plate can vary from about .016 to about .022 of an inch in thickness. Also, the invention is applicable to electrotype shells other than XX shells, its application in the backing of X and XXX shells being contemplated within the scope of the'invention.

- It is readily apparent from the results attained by practice of the invention according to the examples set out above that both the thickness and composition of the insert plate are important factors to be considered with regard to the final results to be attained. By selecting the proper thickness and composition of the insert plate with relation to the thickness of the electrotype shell, the dimensional change in the shell, that is the amount of permanent expansion or contraction of the shell in the resultant electrotype plate, may be accurately controlled or may be eliminated entirely, as desired. Where the term dimensional change is employed in the claims, it is intended to cover not only shrinkage or expansion of the shell but also cases wherein the dimensional change is zero.

Inthe foregoing, the preferred method of practicing the invention, wherein the insert plate is pressed into firm contact with the back of the shell, has been illustrated and described. It has been found that satisfactory results are also ob tained by employing an insert plate of greater thickness and maintaining the'same in spaced relation to the back of the shell while the backing metal solidifies. In this modified form of the invention, the same procedure of tinning the shell and plate is followed. The insert plate is then immersed in the molten backing metal and held in spaced relation with respect to the back of the shell while the backing metal cools.

As an example of the modified process, a copper insert plate .038 of an inch in thickness, tinned on both sides, is immersed in the molten backing metal previously poured on the back of a XX shell to a depth of H of an inch and is maintained spaced about of an inch from the back of the shell during solidification of the backing metal. There will be no dimensional change in the shell due to the backing operation.

While a preferred embodiment of the invention has been illustrated and preferred methods of carrying the same into effect have been described by way of example, it will be understood that modifications thereof are contemplated without departing from the spirit of the invention within the scope of the appended claims.

I claim:

1. A method of controlling dimensional change in an electrotype shell in the production of electrotype printing plates which comprises pouring molten backing metal on the back of an electrotype shell, immersing in the molten backing metal a metallic member of a composition and thickness selected to produce a predetermined. dimensional change in the shell, positioning said member adjacent the back of the shell with an intermediate bonding layer of molten backing metal between said member and the back of the shell and maintaining said member so positioned adjacent the back of the shell during cooling of the backing metal.

2. A method of producing electrotype printing plates comprising pouring molten backing metal on an electrotype shell, immersing in the molten backing metal a metal sheet of a composition and thickness selected to produce a predetermined dimensional change in the shell, positioning said sheet adjacent the back of said shell with an intermediate bonding layer of molten backing metal between said sheet and the back of the shell and cooling the backing metal with said sheet immersed therein and positioned adjacent the back of said shell.

3. A method of controlling dimensional change in an electrotype shell in the production of electrotype printing plates which comprises pouring molten backing metal on the back of an electrotype shell immersing in the molten backing metal a metallic member of a composition and thickness selected substantially to neutralize shrinkage of said shell positioning said member against the back of said shell with an intermediate bonding layer of molten backing metal between said member and the back of the shell, and maintaining said member so positioned against said shell during cooling of the backing metal.

4. A method of controlling dimensional change in an electrotype shell in the production of electrotype printing plates comprising pouring molten backing metal on the back of an electrotype shell having a thickness 01' the order of .020

of an inch, immersing in the molten backing metal a copper sheet having a thickness of the order of .019 to .020 of an inch, and maintaining said sheet in contact with the back of said shell during solidification of the backing metal.

5. A method oi controlling dimensional change in an electrotype shell in the production of electrotype printing plates comprising pouring molten backing metal on the back of a shell having a thickness oi. the order of .020 of an inch, immersing in the molten backing metal a brass sheet having a thickness of the order of .020 of an inch, positioning said sheet against the back of said shell, and maintaining the position 01' shell and sheet during solidificaton of the backing metal.

6. A method of controlling dimensional change in an electrotype shell in the production of electrotype printing plates which comprises pouring molten backing metal on the back on an electrotype shell, immersing in the molten bacldng metal a metal sheet of the order of from .015 to .022 of an inch in thickness, positioning said sheet against the back or said shell with an intermediate bonding layer of molten backing metal between the sheet and the back of the shell and maintaining said sheet against the back of said shell during solidification of the backing metal.

7. A method or controlling dimensional change in an electrotype shell in the production 'of electrotype printing plates which comprises pouring molten backing metal on the back of said shell, immersing in said molten backing metal a metallic sheet of a composition and thickness selected to produce a predetermined expansion of said shell, positioning said sheet against the back of said shell with the molten backing metal forming a bonding layer between said sheet and the back of the shell, and maintaining said sheet in contact with the back of said shell during solidification oi the backing metal.

8. A meth'od oi controlling dimensional change in an electrotype shell in the production 01' electrotype printing plates which comprises pouring molten backing metal on the back of an electrotype shell having a thickness of the order of .020 of an inch, immersing in the molten backing metal a phosphor bronze sheet having a thickness of the order of .020 of an inch, positioning said phosphor bronze sheet against the back of said shell, and maintaining the shell and sheet in contact until the backing metal solidifies.

9. An electrotype printing plate comprising an electrotype shell, 9. cast metal backing united to said shell, a metal sheet, of a composition and thickness selected to produce a predetermined dimensional change inthe electrotype shell during the production of the printing plate, embedded in said cast metal backing and positioned adjacent the back of said shell, and a bonding layer of backing metal between said sheet and the back of said shell. .10. An electrotype printing plate comprising an electrotype shell oi the order of .020 01' an inch in thickness, 8. cast metal backing united to said shell, and a metal sheet 01 the order of .015 to metal backing and back of said shell.

11. An electrotype printing plate comprising an electrotype shell of the order oi .020 of an inch in thickness, a cast metal backing united to said shell, and a copper sheet of the order of .019 to ,020 oi an inch in thickness embedded in said cast metal backing and positioned in contact with the back of said shell.

12. An electrotype printing plate comprising an electrotype shell of the order of .020 of an inch in thickness, a cast metal backing united to said shell, and a half hard brass sheet of the order of .020 of an inch in thickness embedded in said castmetal backing and positioned in contact with the back of said shell.

13. An electrotype printing plate comprising an electrotype shell of the order 01' .020 of an inch in thickness,a cast metal backing united to said shell, and a phosphor bronze sheet of the order of .020 of an inch in thickness, embedded in said cast metal backing and positioned in contact with the back of said shell.

14. A method 01' producing electrotype printing plates comprising pouring molten backing metal on an electrotype shell, immersing in the molten backing metal a metal sheet of a composition and thickness selected to produce a predetermined dimensional change in the shell, po-. sitioning said sheet in spaced relation to theback oi said shell with an intermediate layer of molten backing metal between said sheet and the back of the shell and cooling the backing metal with said sheet immersed therein and positioned in spaced relation to the back oi the shell.

15. A method of controlling dimensional change in an electrotype shell in the production of electrotype printing plates comprising pouring molten backing metal on the back of an electrotype shell having a thickness of the order of .020 01' an positioned in contact with the .022 of an inch in thickness embedded in said cast 29 inch, immersing in the molten backing metal a copper sheet having a thickness of the order of v .038 of an inch, and maintaining said sheet spaced of an inch.

BENJAMIN F. A'IWOOD. 

